The Cytology Core provides technical support to many other investigators, with a common focus on the anatomical study of gap junctions, using BM techniques, freeze fracture, and LM and EM immunocytochemistry. A wide variety of tissues are currently under study from both vertebrates and invertebrates. In cooperation with Dr. Hertzberg, BM an immunofluorescence protocols are tested for new anti- connexin antibodies, each of which needs to be tested for the optimal degree of fixation which can be tolerated by that antigen-antibody complex before immunogenicity is lost. Over the past several years the Core has developed protocols for the immunolabelling of Cx32, Cx26, Cx43, Cx33, Cx37 and Cx40. In addition, the core serves as a resource for training other personnel in less specialized histochemical techniques, particularly immuno-fluorescence, which are widely used by the various projects. Several techniques are currently under development that should be useful to current and future projects, including cryothin sections and in situ hybridization for EM.